Conventionally, medical image diagnosis apparatuses, such as ultrasonic diagnosis apparatuses, X-ray computed tomography (CT) apparatuses, and magnetic resonance imaging (MRI) apparatuses, have been in practical use, including apparatuses capable of generating three-dimensional medical image data (hereinafter, referred to as volume data). In recent years, virtual endoscopy (VE) images with which the inside of a lumen can be observed are generated and displayed from volume data including the lumen. Examples of the method for displaying such a virtual endoscopy image include displaying the virtual endoscopy image as a moving image by moving a viewpoint along a running line (a core line) of the lumen. Hereinafter, such display is referred to as “display of a VE moving image”.
For example, a VE moving image of a mammary gland is display by ultrasonic diagnosis apparatuses, which are used for examinations and diagnoses of various types of body tissues because they have advantageous effects, such as non-invasive characteristics, compared to other medical image diagnosis apparatuses. Display of a VE moving image of a mammary gland is a function expected to serve as a virtual mammary duct endoscopy. Because of structural characteristics of a mammary gland, a plurality of mammary ducts are present in volume data including the mammary gland and each branch off repeatedly.
In an actual mammary duct endoscopy, an endoscope is inserted into a mammary duct that secretes milk, and all the branches included in the mammary duct are observed, by which it is identified which branch secretes the milk. In other words, in an actual mammary duct endoscopy, an examiner repeats an operation of moving the endoscope back to a branch point, thereby observing all the branches. Similarly to this, it is necessary to observe all the branches included in a mammary duct that secretes milk also in a virtual mammary duct endoscopy.
In conventional display of a VE moving image, however, an examiner typically refers to a multi-planer reconstruction (MPR) image obtained by cutting volume data along a section passing through a position of a viewpoint, thereby detecting a current viewpoint position of the virtual endoscopy image, for example. In other words, in the conventional display of a VE moving image, the relation between the entire structure of a mammary duct and the current viewpoint position and determination to complete the observation depend on memory of the examiner. As a result, in an examination carried out by the conventional display of a VE moving image, the examination may possibly be completed despite the presence of yet-to-be-observed branches because of an oversight or a misunderstanding of the examiner.
The possibility that the examination may be completed despite the presence of yet-to-be-observed branches typically occurs in display of a VE moving image of a branching lumen. Furthermore, the possibility that the examination may be completed despite the presence of yet-to-be-observed branches also occurs in the use of volume data acquired by a medical image diagnosis apparatus other than ultrasonic diagnosis apparatuses.